This invention relates to compressor systems, and more particularly to an oil separator for use in the crankcase of an accessible hermetic refrigerant compressor.
In refrigerating systems using self-contained motor compressor units in which the returning refrigerant is used to cool the motor it is important that the crankcase pressure be maintained at a sufficiently low level relative to the rest of the system to permit return of lubricant collected in the motor compartment to the crankcase. During the starting period of the compressor, refrigerant mixed with the lubricant in the crankcase will foam and the foamed oil will tend to be drawn from the crankcase. Typically check valve passages have been provided for permitting pressure relief from the crankcase while preventing loss of lubricant. However, additional problems have occurred in that the refrigerant being supplied to the intake manifold may back up through such passages to maintain or even increase the crankcase pressure. Piston blow-by gas is another factor making it difficult to maintain crankcase pressure at a sufficiently low level.
It is an object of the present invention to overcome the disadvantages of previously known means for obtaining crankcase pressure reduction in refrigerating units of this type and to provide a novel and improved construction for venting the crankcase and maintaining lubricant supply in an efficient and reliable manner.
It is a further object of this invention to allow for the venting of piston blow-by gas while preventing the loss of entrained oil.
During a flooded start transient the crankcase is filled with liquid refrigerant. The rotating crank generates a great deal of heat from drag loss and causes the liquid to flash. It is another object of the present invention to allow this gas to vent off at a metered rate while centrifugally separating the oil.
During normal operation, the crankcase oil separator inlet of the present invention is oriented relative to the crank throw to prevent piston blow-by gas from carrying away entrained oil. This results in a lower system oil circulation rate and reduced compressor oil pump-out rate. During a flooded start or defrost condition, the crankcase oil separator provides a centrifugal oil separating capability to keep oil from being washed out when liquid refrigerant flashes. When a flooded start occurs an orifice disk closes and meters flow at a rate that can be handled by the crankcase oil separator. The larger entrained oil droplets are removed from the flow and gravity drained back out the lower part of the inlet into the oil sump.
There are several advantages to the present invention. First, the reliability of the compressor is improved by reducing the chance of a lubrication related failure due to oil loss. Second, the possibility of slugging during a flooded start is greatly reduced by oil retention. Third, the amount of running time spent at low oil pressure due to refrigerant in the lube system during flooded start is reduced. Fourth, the crankcase oil separator allows crankcase pressure to be vented off relatively quickly without major oil loss. The reduced oil pump-out rate is particularly important on systems with long piping lines where oil is slow to return.